Examination of methylphenidate-mediated behavior regulation by glycogen synthase kinase-3 in mice

A multi-omics analysis reveals vitamin D supplementation since childhood modulates molecules for signal transductions in the mouse striatum

Vitamin D is a critical fat-soluble vitamin for the nervous system. Research suggests a potential link between vitamin D deficiency and attention-deficit hyperactivity disorder (ADHD), particularly in children and adolescents. The core symptoms of ADHD are associated with deficits in striatal functions, and maintaining sufficient levels of vitamin D may help prevent or alleviate ADHD symptoms. However, the molecular changes in the striatum caused by vitamin D supplementation that may contribute to the brain processes linked to ADHD symptoms remain unclear. In this study, we established a mouse model fed diets with three different dose gradients of vitamin D3 (0, 500, and 2000 IU/kg·day) from postnatal day 21 (P21) to 14 weeks of age. Striatal tissues from mice with gradient vitamin D3 intake were subjected to reduced representation bisulfite sequencing (RRBS), RNA-sequencing, and neurotransmitter profiling by liquid chromatography-mass spectrometry (LC-MS). Our findings indicate that vitamin D supplementation since childhood influenced the overall landscape of DNA methylations and the expression of many genes involved in critical neurological functions in a dose-dependent manner. Additionally, our data demonstrate how vitamin D modulated neuropeptide signaling pathways, as well as cholinergic and dopaminergic synapses in the striatum, through an orchestrated mechanism involving epigenetic and transcriptional regulations. Furthermore, we observed a synergistic effect of vitamin D on dopamine release following acute methylphenidate injection into our mouse model. In summary, this study provides mechanistic insights into how dietary vitamin D supplementation since childhood can modulate specific signal transductions among striatal cells, underscoring the importance of vitamin D supplementation for ADHD management.

Behavioral, Neurochemical and Developmental Effects of Chronic Oral Methylphenidate: A Review

The majority of animal studies on methylphenidate (MP) use intraperitoneal (IP) injections, subcutaneous (SC) injections, or the oral gavage route of administration. While all these methods allow for delivery of MP, it is the oral route that is clinically relevant. IP injections commonly deliver an immediate and maximum dose of MP due to their quick absorption. This quick-localized effect can give timely results but will only display a small window of the psychostimulant's effects on the animal model. On the opposite side of the spectrum, a SC injection does not accurately represent the pathophysiology of an oral exposure because the metabolic rate of the drug would be much slower. The oral-gavage method, while providing an oral route, possesses some adverse effects such as potential animal injury and can be stressful to the animal compared to voluntary drinking. It is thus important to allow the animal to have free consumption of MP, and drinking it to more accurately mirror human treatment. The use of a two-bottle drinking method allows for this. Rodents typically have a faster metabolism than humans, which means this needs to be considered when administering MP orally while reaching target pharmacokinetic levels in plasma. With this oral two-bottle approach, the pathophysiological effects of MP on development, behavior, neurochemistry and brain function can be studied. The present review summarizes these effects of oral MP which have important implications in medicine.

From attention-deficit hyperactivity disorder to sporadic Alzheimer's disease-Wnt/mTOR pathways hypothesis

Alzheimer's disease (AD) is the most common neurodegenerative disorder with the majority of patients classified as sporadic AD (sAD), in which etiopathogenesis remains unresolved. Though sAD is argued to be a polygenic disorder, apolipoprotein E (APOE) ε4, was found three decades ago to pose the strongest genetic risk for sAD. Currently, the only clinically approved disease-modifying drugs for AD are aducanumab (Aduhelm) and lecanemab (Leqembi). All other AD treatment options are purely symptomatic with modest benefits. Similarly, attention-deficit hyperactivity disorder (ADHD), is one of the most common neurodevelopmental mental disorders in children and adolescents, acknowledged to persist in adulthood in over 60% of the patients. Moreover, for ADHD whose etiopathogenesis is not completely understood, a large proportion of patients respond well to treatment (first-line psychostimulants, e.g., methylphenidate/MPH), however, no disease-modifying therapy exists. Interestingly, cognitive impairments, executive, and memory deficits seem to be common in ADHD, but also in early stages of mild cognitive impairment (MCI), and dementia, including sAD. Therefore, one of many hypotheses is that ADHD and sAD might have similar origins or that they intercalate with one another, as shown recently that ADHD may be considered a risk factor for sAD. Intriguingly, several overlaps have been shown between the two disorders, e.g., inflammatory activation, oxidative stress, glucose and insulin pathways, wingless-INT/mammalian target of rapamycin (Wnt/mTOR) signaling, and altered lipid metabolism. Indeed, Wnt/mTOR activities were found to be modified by MPH in several ADHD studies. Wnt/mTOR was also found to play a role in sAD and in animal models of the disorder. Moreover, MPH treatment in the MCI phase was shown to be successful for apathy including some improvement in cognition, according to a recent meta-analysis. In several AD animal models, ADHD-like behavioral phenotypes have been observed indicating a possible interconnection between ADHD and AD. In this concept paper, we will discuss the various evidence in human and animal models supporting the hypothesis in which ADHD might increase the risk for sAD, with common involvement of the Wnt/mTOR-pathway leading to lifespan alteration at the neuronal levels.

Neuroprotective Properties of Minocycline Against Methylphenidate-Induced Neurodegeneration: Possible Role of CREB/BDNF and Akt/GSK3 Signaling Pathways in Rat Hippocampus

Neurodegeneration is a side effect of methylphenidate (MPH), and minocycline possesses neuroprotective properties. This study aimed to investigate the neuroprotective effects of minocycline against methylphenidate-induced neurodegeneration mediated by signaling pathways of CREB/BDNF and Akt/GSK3. Seven groups of seventy male rats were randomly distributed in seven groups (n = 10). Group 1 received 0.7 ml/rat of normal saline (i.p.), and group 2 was treated with MPH (10 mg/kg, i.p.). Groups 3, 4, 5, and 6 were simultaneously administered MPH (10 mg/kg) and minocycline (10, 20, 30, and 40 mg/kg, i.p.) for 21 days. Minocycline alone (40 mg/kg, i.p.) was administrated to group 7. Open field test (OFT) (on day 22), forced swim test (FST) (on day 24), and elevated plus maze (on day 26) were conducted to analyze the mood-related behaviors; hippocampal oxidative stress, inflammatory, and apoptotic parameters, as well as the levels of protein kinase B (Akt-1), glycogen synthase kinase 3 (GSK3), cAMP response element-binding protein (CREB), and brain-derived neurotrophic factor (BDNF), were also assessed. Furthermore, localization of total CREB, Akt, and GSK3 in the DG and CA1 areas of the hippocampus were measured using immunohistochemistry (IHC). Histological changes in the mentioned areas were also evaluated. Minocycline treatment inhibited MPH-induced mood disorders and decreased lipid peroxidation, oxidized form of glutathione (GSSG), interleukin 1 beta (IL-1β), alpha tumor necrosis factor (TNF-α), Bax, and GSK3 levels. In the contrary, it increased the levels of reduced form of glutathione (GSH), Bcl-2, CREB, BDNF, and Akt-1 and superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR) activities in the experimental animals' hippocampus. IHC data showed that minocycline also improved the localization and expression of CREB and Akt positive cells and decreased the GSK3 positive cells in the DG and CA1 regions of the hippocampus of MPH-treated rats. Minocycline also inhibited MPH-induced changes of hippocampal cells' density and shape in both DG and CA1 areas of the hippocampus. According to obtained data, it can be concluded that minocycline probably via activation of the P-CREB/BDNF or Akt/GSK3 signaling pathway can confer its neuroprotective effects against MPH-induced neurodegeneration.

Methylphenidate administration promotes sociability and reduces aggression in a mouse model of callousness

RATIONALE

Deficits in empathy constitute a distinctive feature of several psychopathologies, including conduct disorder (CD). The co-occurrence of callous-unemotional (CU) traits, excess rates of aggression and violation of societal norms confers specific risk for adult psychopathy. To date, the off-label use of methylphenidate (MPH) constitutes the drug treatment of choice.

OBJECTIVES

Herein, we tested the therapeutic potential of MPH in a recently devised mouse model recapitulating the core phenotypic abnormalities of CD.

METHODS

Two subgroups of BALB/cJ male mice exhibiting opposite profiles of emotional contagion (i.e. socially transmitted adoption of another's emotional states) were investigated for reactive aggression, sociability, attention control, anxiety-related behaviours and locomotor activity, in response to MPH administration (0.0, 3.0 or 6.0 mg/kg).

RESULTS

Our data indicate that mice selected for excess callousness exhibit phenotypic abnormalities isomorphic to the symptoms of CD: stability of the low emotional contagion trait, increased aggression and reduced sociability. In accordance with our predictions, MPH reduced aggression and increased sociability in callous mice; yet, it failed to restore the low responsiveness to the emotions of a conspecific in pain, isomorphic to CU traits.

CONCLUSIONS

Although our data support the notion that MPH may contribute to the management of excess aggression in CD patients, additional studies shall identify specific treatments to target the callousness domain. The latter, unaffected by MPH in our experimental model, demands focused consideration whereby it constitutes a specifier associated with a worse prognosis.

Glycogen synthase kinase-3β genetic polymorphisms and insomnia in depressed patients: A prospective study

BACKGROUND

80-90% of patients with Major Depressive Episode (MDE) experience insomnia and up-to 50% severe insomnia. Glycogen Synthase Kinase-3β (GSK3B) is involved both in mood regulation and circadian rhythm. Since GSK3B polymorphisms could affect protein levels or functionality, we investigated the association of GSK3B polymorphisms with insomnia in a sample of depressed patients treated with antidepressants.

METHODS

In this 6-month prospective real-world treatment study in psychiatric settings (METADAP), 492 Caucasian patients requiring a new antidepressant treatment were included and genotyped for five GSK3B Single Nucleotide Polymorphisms (SNPs) (rs6808874, rs6782799, rs2319398, rs13321783, rs334558). Insomnia and MDE severity were rated using the Hamilton Depression Rating Scale (HDRS). Bi- and multivariate analyses were performed to assess the association between GSK3B SNPs and insomnia (main objective). We also assessed their association with MDE severity and HDRS response/remission after antidepressant treatment.

RESULTS

At baseline severe insomnia was associated with the GSK3B rs334558 minor allele (C+) [OR=1.81, CI95%(1.17-2.80), p=0.008]. GSK3B rs334558 C+ had greater insomnia improvement after 6 months of antidepressant treatment (p=0.007, β=0.17, t=2.736). No association was found between GSK3B SNPs and MDE baseline severity or 6-month response/remission.

CONCLUSION

GSK3B rs334558 was associated with insomnia but not with MDE severity in depressed patients. Targeting GSK3B in patients with MDE and a severe insomnia could be a way to improve their symptoms with greater efficiency. And it should be further studied whether the GSK3B-insomnia association may fit into the larger picture of mood disorders.

Wnt signaling networks in autism spectrum disorder and intellectual disability

Background

Genetic factors play a major role in the risk for neurodevelopmental disorders such as autism spectrum disorders (ASDs) and intellectual disability (ID). The underlying genetic factors have become better understood in recent years due to advancements in next generation sequencing. These studies have uncovered a vast number of genes that are impacted by different types of mutations (e.g., de novo, missense, truncation, copy number variations).

Abstract

Given the large volume of genetic data, analyzing each gene on its own is not a feasible approach and will take years to complete, let alone attempt to use the information to develop novel therapeutics. To make sense of independent genomic data, one approach is to determine whether multiple risk genes function in common signaling pathways that identify signaling “hubs” where risk genes converge. This approach has led to multiple pathways being implicated, such as synaptic signaling, chromatin remodeling, alternative splicing, and protein translation, among many others. In this review, we analyze recent and historical evidence indicating that multiple risk genes, including genes denoted as high-confidence and likely causal, are part of the Wingless (Wnt signaling) pathway. In the brain, Wnt signaling is an evolutionarily conserved pathway that plays an instrumental role in developing neural circuits and adult brain function.

Conclusions

We will also review evidence that pharmacological therapies and genetic mouse models further identify abnormal Wnt signaling, particularly at the synapse, as being disrupted in ASDs and contributing to disease pathology.

Multiple Drug Treatments That Increase cAMP Signaling Restore Long-Term Memory and Aberrant Signaling in Fragile X Syndrome Models

Fragile X is the most common monogenic disorder associated with intellectual disability (ID) and autism spectrum disorders (ASD). Additionally, many patients are afflicted with executive dysfunction, ADHD, seizure disorder and sleep disturbances. Fragile X is caused by loss of FMRP expression, which is encoded by the FMR1 gene. Both the fly and mouse models of fragile X are also based on having no functional protein expression of their respective FMR1 homologs. The fly model displays well defined cognitive impairments and structural brain defects and the mouse model, although having subtle behavioral defects, has robust electrophysiological phenotypes and provides a tool to do extensive biochemical analysis of select brain regions. Decreased cAMP signaling has been observed in samples from the fly and mouse models of fragile X as well as in samples derived from human patients. Indeed, we have previously demonstrated that strategies that increase cAMP signaling can rescue short term memory in the fly model and restore DHPG induced mGluR mediated long term depression (LTD) in the hippocampus to proper levels in the mouse model (McBride et al., 2005; Choi et al., 2011, 2015). Here, we demonstrate that the same three strategies used previously with the potential to be used clinically, lithium treatment, PDE-4 inhibitor treatment or mGluR antagonist treatment can rescue long term memory in the fly model and alter the cAMP signaling pathway in the hippocampus of the mouse model.

GSK3β isoform-selective regulation of depression, memory and hippocampal cell proliferation

Abnormally active glycogen synthase kinase-3 (GSK3) contributes to pathological processes in multiple psychiatric and neurological disorders. Modeled in mice, this includes increasing susceptibility to dysregulation of mood-relevant behaviors, impairing performance in several cognitive tasks and impairing adult hippocampal neural precursor cell (NPC) proliferation. These deficits are all evident in GSK3α/β knockin mice, in which serine-to-alanine mutations block the inhibitory serine phosphorylation regulation of both GSK3 isoforms, leaving GSK3 hyperactive. It was unknown if both GSK3 isoforms perform redundant actions in these processes, or if hyperactivity of one GSK3 isoform has a predominant effect. To test this, we examined GSK3α or GSK3β knockin mice in which only one isoform was mutated to a hyperactive form. Only GSK3β, not GSK3α, knockin mice displayed heightened vulnerability to the learned helplessness model of depression-like behavior. Three cognitive measures impaired in GSK3α/β knockin mice showed differential regulation by GSK3 isoforms. Novel object recognition was impaired in GSK3β, not in GSK3α, knockin mice, whereas temporal order memory was not impaired in GSK3α or GSK3β knockin mice, and co-ordinate spatial processing was impaired in both GSK3α and GSK3β knockin mice. Adult hippocampal NPC proliferation was severely impaired in GSK3β knockin mice, but not impaired in GSK3α knockin mice. Increased activity of GSK3β, in the absence of overexpression or disease pathology, is sufficient to impair mood regulation, novel object recognition and hippocampal NPC proliferation, whereas hyperactive GSK3α individually does not impair these processes. These results show that hyperactivity of the two GSK3 isoforms execute non-redundant effects on these processes.

Glycogen synthase kinase-3β inhibition in the medial prefrontal cortex mediates paradoxical amphetamine action in a mouse model of ADHD

Psychostimulants show therapeutic efficacy in the treatment of attention-deficit hyperactivity disorder (ADHD). It is generally assumed that they ameliorate ADHD symptoms via interfering with monoaminergic signaling. We combined behavioral pharmacology, neurochemistry and molecular analyses to identify mechanisms underlying the paradoxical calming effect of amphetamine in low trait anxiety behavior (LAB) mice, a novel multigenetic animal model of ADHD. Amphetamine (1 mg/kg) and methylphenidate (10 mg/kg) elicited similar dopamine and norepinephrine release in the medial prefrontal cortex (mPFC) and in the striatum of LAB mice. In contrast, amphetamine decreased, while methylphenidate increased locomotor activity. This argues against changes in dopamine and/or norepinephrine release as mediators of amphetamine paradoxical effects. Instead, the calming activity of amphetamine corresponded to the inhibition of glycogen synthase kinase 3β (GSK3β) activity, specifically in the mPFC. Accordingly, not only systemic administration of the GSK3β inhibitor TDZD-8 (20 mg/kg), but also local microinjections of TDZD-8 and amphetamine into the mPFC, but not into the striatum, decreased locomotor activity in LAB mice. Amphetamine effects seem to depend on NMDA receptor signaling, since pre- or co-treatment with MK-801 (0.3 mg/kg) abolished the effects of amphetamine (1 mg/kg) on the locomotion and on the phosphorylation of GSK3β at the level of the mPFC. Taken together, the paradoxical calming effect of amphetamine in hyperactive LAB mice concurs with a decreased GSK3β activity in the mPFC. This effect appears to be independent of dopamine or norepinephrine release, but contingent on NMDA receptor signaling.

Hyperactivity: glycogen synthase kinase-3 as a therapeutic target

The diagnosis of hyperactivity-associated disorders has increased within the past few years. The prevalence of hyperactivity-associated disorders is indicative of the need to more fully understand the underlying causes and to develop improved therapeutic interventions. There is increasing evidence that glycogen synthase kinase-3 (GSK3) mediates locomotor hyperactivity in a number of animal models, and therefore may be a potential target for therapeutic intervention in hyperactivity-associated behaviors. In this review, we discuss 1) the effect of manipulations of GSK3 in the absence of drugs and disorders on locomotor activity, 2) the role of GSK3 in drug-induced hyperactivity in rodents, and 3) regulation of locomotor activity by GSK3 in transgenic mouse models related to specific disorders. These studies link GSK3 regulation and activity to hyperactivity-associated behaviors and disease pathologies.